These spreader settings are suggestions and are not a replacement for properly calibrating your spreader. See your spreader manufacturer's guide for proper spreader calibration. To use this guide as a starting point: Look at your spreader and find the range of settings* for your model. Then reference the chart to find an approximate spreader rate for your application.
Calculating the appropriate rates for your fertilizer application can be confusing for those who don't do it regularly. Here are some helpful formulas and related information that can help get your acre squared away.
Your Spreader's Range
5 lbs/1,000 sq ft
3 lbs/1,000 sq ft
4 lbs/1,000 sq ft
*If your spreader uses an alphabetical system rather than numerical; convert letters to numbers to find your settings. For example: "A" would become 1, "B" equals 2, and so on. Example: For a spreader that has settings of A-R you would refer to the chart for a spreader with a range of 1-18, or the next closest number set.
How to find the actual amount of a nutrient in a 50 lb. bag of fertilizer.
Ever wonder exactly how many pounds of a given nutrient are in one bag of fertilizer? While the all the numbers on the front of the bag don't always look like they all add up they all serve a very specific purpose. Using them you can easily calculate exactly how many pounds of a given nutrient are in a bag.
The three primary numbers listed on any fertilizer bag are listed as the percentage of the total weight of the bag and are always listed in the order of Nitrogen (N), then Phosphorous (P), and finally Potassium (K).
To find the actual amount by weight of these nutrients you just have to do some simple math.
Convert the nutrients number by dividing by 100.
Take that result and multiply by the bag weight, in this case 50 lbs.
For example, let's use a blend of 20-6-16 is 20% Nitrogen, 6% Phosphorous, and 16% Potassium. Our 20-6-16; 20 divided by 100 gives us .2. Taking that result of .2 and multiplying it by 50 gives us 10. That means there is 10 pounds of Nitrogen in this particular blend. The same principle can be used for all the other nutrients in the blend.
How to find the number of bags needed for a desired application rate.
So, you want to fertilize your lawn. Great! After speaking with your Spring Valley dealer you find that perfect blend for your application. Now all you need to do is place the order. But how many bags are you going to need to cover your lawn at the recommended application rate?
To do the calculation you first need two pieces of information. The first is the target application rate, for example .75 lbs. of N/ 1,000 sq. ft. The second is the total area you will be applying the fertilizer to, for example: 40,000 sq. ft. Using this information you can find the total pounds of N you need to cover your lawn by multiplying your application rate by the number of square feet, then divide by 1,000.
So in our example: .75 x 40,000 = 30,000. 30,000 divided by 1,000 yields the number of pounds of nitrogen needed, in this case 30. So now we know how many pounds of nitrogen we need to cover our 40,000 sq. ft. lawn, now we just need to figure out how many bags of fertilizer we need to give us our 30 pounds of N. To do this just take your total nitrogen needs (30 in our example) and divide it by the amount of nitrogen in each bag. Using our example from above (How to find the actual amount of a nutrient section) of 10 lbs. N per bag we then are left with the calculation 30/10 which gives us an answer of 3 bags needed to apply .75 lbs. N on 40,000 sq. ft.